Integrated power amplifier module with power sensor

ABSTRACT

A power amplifier module for amplifying radio frequency signals includes first, second, third and fourth corner ground pads positioned at each corner of the power amplifier module; a radio frequency input pad positioned between the first and second corner ground pads; a radio frequency output pad positioned between the third and fourth corner ground pads; and a power amplifier circuit centrally positioned on the power amplifier module, the power amplifier having an input coupled to the radio frequency input pad and an output coupled to the radio frequency output pad.

[0001] This application is a continuation of application Ser. No.10/385,058 filed on Mar. 9, 2003, titled “Power Amplifier Module forWireless Communication Devices”, which in turn claims priority toProvisional Application Ser. No. 60/397,261, filed on Jul. 19, 2002,titled “Power Amplifier Modules for Wireless LAN Applications”, thecontents of which are incorporated by reference. The application is alsorelated to the commonly assigned U.S. patent application Ser. No.10/041,863, filed on Oct. 22, 2001, titled “Multilayer RF AmplifierModule”, by Wang, et al., and the commonly assigned and concurrentlyfiled U.S. patent application “Accurate Power Sensing Circuit for PowerAmplifiers” by Ichitsubo et al. The disclosures of these relatedapplications are incorporated herein by reference.

RELATED APPLICATION

[0002] The present invention is related to the commonly assigned U.S.patent application Ser. No. 10/041,863, filed on Oct. 22, 2001, titled“Multilayer RF Amplifier Module”, by Wang, et al., and the commonlyassigned and concurrently filed U.S. patent application “Accurate PowerSensing Circuit for Power Amplifiers” by Ichitsubo et al. Thedisclosures of these related applications are incorporated herein byreference.

BACKGROUND

[0003] The present invention relates to radio frequency (RF) poweramplifiers (PA) module. Portable devices such as laptop personalcomputers (PC), Personal Digital Assistant (PDA) and cellular phoneswith wireless communication capability are being developed in everdecreasing size for convenience of use. Correspondingly, the electricalcomponents thereof must also decrease in size while still providingeffective radio transmission performance. However, the substantiallyhigh transmission power associated with RF communication increases thedifficulty of miniaturization of the transmission components.

[0004] A major component of the wireless communication device is theradio frequency PA. The PA is conventionally in the form of asemiconductor integrated circuit (IC) chip or die in which signalamplification is effected with substantial power. The amplifier chip isinterconnected in a circuit with certain off-chip components such asinductors, capacitors, resistors, and transmission lines used forcontrolling operation of the amplifier chip and providing impedancematching of the input and output RF signals. The amplifier chip andassociated components are typically assembled, on a printed circuitboard (PCB) in which the components are interconnected by layers printedmetal circuits and layers of dielectric substrates. One importantconsideration for wireless devices is to properly control the qualityand power level of the amplified RF signals to be transmitted. Inparticular for high data rate wireless communications, the amplificationof RF signals is required to be linear over a wide signal power rangeand over a given frequency range. Preferably the amplification isreduced or increased according to input RF signal, transmittance rangeand data rate so that power consumption can be optimized.

[0005] Among important considerations in wireless devices are thegrounding and RF signal isolation. A power amplifier typically has highcurrent flowing through the circuit.

[0006] A non-zero impedance in the circuit can easily induce a voltage,potentially injecting unwanted noise into the RF system. Poor circuitboard grounding can thus cause unintended feedback and oscillations. Theground current paths and the current handling capability of componentshave to be considered carefully. Since RF circuits operate at high powerand high signal frequencies, electromagnetic radiation created caninterfere with other components of the wireless communication device, orwith other electronic devices.

[0007] Another significant consideration in the miniaturization of RFamplifier circuits is the required impedance matching for the input andoutput RF signals of the amplifier. Input and output impedance matchingcircuits typically include capacitors, resistors, and inductors inassociated transmission lines or micro strips for the RF signals intoand out of the amplifier chip. However, these impedance matchingcircuits may require specifically tailored off-chip components locatedremotely from the amplifier IC chip. Accordingly, the applicationcircuitry must include many electrical input and output terminals orbonding Pins to which the corresponding portions of the off-chipimpedance matching circuits are separately joined. This increases thedifficulty of assembly and required size of the associated components,and affects the overall manufacturability of the portable devices.

SUMMARY

[0008] In one aspect, the present invention provides a power amplifiermodule for amplifying radio frequency signals, comprising: a) a radiofrequency power amplifier including one or more semiconductortransistors, adapted to receive an input radio frequency signal and aprocessed power-sensing control signal, and to output an amplified radiofrequency signal; b) a power-sensing circuit adapted to receive theamplified radio frequency signal and to output the power-sensing controlsignal, and c) a control logic that receives and processes thepower-sensing control signal, and outputs a processed power-sensingcontrol signal in response to a quality or a magnitude of the amplifiedradio frequency signal.

[0009] The PA module disclosed in this invention is a linear amplifierwhich provides good linearity and low harmonics over a wide frequencyrange covering from several megahertz (MHZ) to tens of gigahertz (GHZ)by the feedback control based on the qualities and power level of theamplified radio frequency signal. Specifically, high orderinter-modulation distortions are suppressed. The RF amplifier module issuitable to applications in various wireless data and voicecommunications standards and protocols, including Global System forMobile Communications (GSM), General Packet Radio Service (GPRS), CodeDivision Multiple Access (CDMA), Wideband CDMA, IEEE 802.11 and others.The PA module in accordance to the present invention especially providesreliable amplification to the Wireless Local Area Network (WLAN)applications.

[0010] In another aspect, a number of electronic components and circuitsare integrated within the RF amplifier module, including impedancematching circuits for input and output RF signals. The RF amplifiermodule is compact and has smaller foot print compared to prior artimplementations. The integrated RF amplifier module can be convenientlydesigned and assembled in a RF transmission device.

[0011] A feature of the present invention is the efficient grounding,shielding and thermal conduction provided in the RF amplifier module.The power amplifier circuit is fabricated on a semiconductor chip havingan electrically conductive base. The RF power amplifier module includesa multi-layer three-dimensional substrate having a bottom metal layeradapted to bond with the printed circuit board (PCB) of a wirelesscommunication device. The substrate has one or more upper layers adaptedto receive the amplifier chip and other off-chip components. The bottomlayer includes grounding metal Pins that are located at the center andat each corner, which is registered and adapted to bond with the circuitpattern on PCB of the wireless communication device. The metal Pins areconnected to the upper layers through the multilayer three-dimensionalsubstrate by a plurality of metal via holes

[0012] Another feature of the PA module in the present invention is thatthe output signal from the power sensing circuit can be used tooptimally control the bias current and operation characteristics of thepower amplifiers. As a result, the PA module provides highly linearoutput power at reduced current consumption.

[0013] Yet another feature of the invention is that the RF amplifierdesign enables manufacturing consistency since the input and outputmatching circuits are included in the module. Common problems related tothe manufacturing tolerance of the matching circuit components aretherefore eliminated. The RF amplifier design is adapted to highfrequency circuitry by utilizing semiconductor materials such as GalliumArsenide Heterojunction Bipolar Transistors (GaAs HBT).

[0014] Additional features and advantages of the invention will be setforth in the description, which follows, and in part will be obviousfrom the description, or may be learned by the practice of theinvention. The features and advantages of the invention may be realizedand obtained by means of the instruments and combinations particularlypointed out in the appended claims. These and other features of thepresent invention will become apparent from the following descriptionand appended claims, or may be learned by the practice of the inventionas set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order that the manner in which the above recited and otheradvantages and features of the invention are obtained, a more particulardescription of the invention briefly described above will be rendered byreference to specific embodiments thereof, which are illustrated, in theappended drawings. Understanding that these drawings depict only typicalembodiments of the invention and are not therefore to be considered tobe limiting of its scope, the invention will be described and explainedwith additional specificity and detail through the use of theaccompanying drawings in which:

[0016] The accompanying drawings, which are incorporated in and form apart of this specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention:

[0017]FIG. 1 is a system diagram of the power amplifier module forwireless communications in accordance to the present invention.

[0018]FIG. 2 is the electrical schematics for the application of thepower amplifier module shown in FIG. 1 in accordance to an embodiment ofthe present invention.

[0019]FIG. 3 illustrates the use of the power amplifier module forwireless communications in accordance to an embodiment of the presentinvention.

[0020]FIG. 4 are the diagrams of the bottom-side footprint of the poweramplifier module and the printed-circuit-board layout of a wirelesscommunication device, on which the power amplifier module is mounted inaccordance to an embodiment of the present invention.

[0021]FIG. 5 is an exemplary substrate layout.

[0022]FIG. 6 is an exemplary electrical response table.

DESCRIPTION OF INVENTION

[0023] Reference will now be made in detail to the preferred embodimentsof the invention, examples of which are illustrated in the accompanyingdrawings. While the invention will be described in conjunction with thepreferred embodiments, it will be understood that they are not intendedto limit the invention to these embodiments. On the contrary, theinvention is intended to cover alternatives, modifications andequivalents, which may be included within the spirit and scope of theinvention as defined by the appended claims. Furthermore, in thefollowing detailed description of the present invention, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present invention. However, it will be obvious toone of ordinary skill in the art that the present invention may bepracticed without these specific details. In other instances, well knownmethods, procedures, components, and circuits have not been described indetail as not to unnecessarily obscure aspects of the present invention.

[0024] The PA module provides a unitary or common component which may beconveniently assembled in a RF transmission device, with correspondinglysimplified assembly, compact 3D size, and enhanced RF amplificationperformance. In accordance with the present invention, the term “module”refers to such a unitary device for wireless communications, comprisingintegrated power amplifiers and other circuitry and auxiliary electroniccomponents.

[0025]FIG. 1 shows a system diagram of the radio frequency PA module 14for wireless communications in accordance to an embodiment of thepresent invention. The PA module is built on a substrate 12, which canbe a multiplayer printed circuit board (PCB), lead frame,lower-temperature co-fired ceramics (LTCC), or other suitable electronicmaterials. The substrate includes metal Pins adapted to receiveconnecting terminals of integrated circuits including the PowerAmplifiers 24, the Bias Circuit 22, the Power Sensor 26, and optionallyControl Logic 28. The Power Amplifiers 24, the Power Sensor 26, the BiasCircuit 22, can be fabricated in an integrated circuit on asemiconductor chip. The Power Amplifiers 24 can be of one or multiplestages. In the particular example shown in FIG. 1, two sequentiallyconnected stages of power transistors are employed. The amplifier ICchip has an electrically conductive metal layer to be bonded to the topmetal layer of the module.

[0026] The PA module 14 can also include, in accordance with anotherfeature of the present invention, input impedance matching circuit 18and output impedance matching circuit 20. The input and output impedancematching network are preferably based on the 50-ohm standard of the RFindustry. Details of impedance matching circuits are described in theabove referenced and commonly assigned U.S. patent application Ser. No.10/041,863, filed on Oct. 22, 2001, titled “Multilayer RF AmplifierModule”, by Wang, et al.

[0027] The Bias Circuit 22 is used to bias individual stage withsuitable current so the amplifiers can operate with minimal signaldistortion. The Bias Circuit receives input from the power controlsignal from the PC port (Pin 4) and can be selected to operate atdifferent settings of idle current using the Vmode port (Pin 10). Inaccordance with the present invention, the mode control signal and thepower-control signal may be dependent at least partially on thepower-sensing signal output from the Power Sensor circuit 26.

[0028] The PA module is integrated with a Power Sensor circuit 26 thatsenses the level of the output power. Details of the power sensorcircuit are disclosed in the above referenced and commonly assigned U.S.patent application “Accurate Power Sensing Circuit for Power Amplifiers”by Ichitsubo et al., the disclosures of which related application areincorporated herein by reference.

[0029] A power amplifier with good linearity generally must maintain aconstant amplification factor, known as “Gain”, which is defined as theratio of the output signal power level to the input signal power level.However, at high output power level, the power amplifier can be drivenclose to saturation and a constant gain becomes difficult to maintain.As a result, the quality of digital communication, commonly measured byError Vector Magnitude (EVM), Bit Error Rate (BER), or Packet Error Rate(PER), degrades at high output power level.

[0030] The Power Sensor 26 receives the amplified radio frequency signalfrom Power Amplifiers 24 and to output a power-sensing control signal.The Control Logic 28 receives and processes the power-sensing controlsignal, and outputs a processed power-sensing control signal to controlPower Amplifiers 24. The processed power-sensing control signal is afunction of a quality or a magnitude of the amplified radio frequencysignal. For example, the Control Logic 28 improves the linearityperformance of power amplifier using the Power Sensor 26 feedbackinternally. By adjusting the bias of the amplifier depending on theactual output power measured by the Power Sensor 26, it reduces thetendency of saturation and maintains a more constant gain. Thus thelinearity of the amplification over a wide range of power is improved.Yet another method of improving the quality of digital communication isto use an external controller to adjust the input RF signal based theknown relationship of digital communication quality to output powerlevel.

[0031] The PA module 14 shown in FIG. 1 can be used in a wide rangewireless communication devices such as cellular phone, mobile computers,and handheld wireless digital devices. The PA module has a miniaturesize of a few millimeters.

[0032]FIG. 2 is the electrical schematics illustrating the applicationof the PA module 14, as shown in FIG. 1, to wireless communications inaccordance to the present invention. The PA module has a plurality ofmetal Pins, namely, Pin 1 through 10 and the Center Ground 210. Pin 1,3, 6 and 8 are adapted to be connected to the electric ground. Pin 2 (RFIN port) is connected through a 50-ohm transmission line 230 to an RFinput signal to be supplied to the Power Amplifiers 24. The output ofthe power amplifier chip 24 is at Pin 7 (RF OUT port), also connected bya 50-ohm transmission line 240 to the antenna stage, possibly with afilter and transmit/receive switch in between. Pin 4 (PC port) receivesa power control signal, while Pin 5 (Vcc port) receives DC power supply.Pin 9 (Psense port) provides a power sensing signal output, while Pin 10(Vmode port) optimally receives a mode control signal. A series resistorR₂ can be used to set the DC voltage to Vmode advantageously dependingon the requirement of linear power output or the characteristics varyingRF signal.

[0033] Typically, The power supply comes from a regulated voltage sourceto the Vcc port. The PA can be switched ON/OFF by presenting a high andlow signal at the PC port. The voltage of high signal the PC port may beoptimally adjusted with an external resistor R1. When it is switched tothe OFF state, the bias to the power amplifier is shut off and thecurrent consumption is reduced to very small.

[0034] In one embodiment, the input impedance matching network 18, theoutput impedance matching network 20, the power amplifiers 24, the biascircuit 22 and the power sensor 26 are integrated on an integratedcircuit (IC). The IC includes top terminals or bonding Pins whichprovide various input and output connections to the internal componentsof the chip. The top terminals are electrically joined to one or more ofthe plates in the substrate 12. In the preferred embodiment, the chipincludes Gallium Arsenide Heterojunction Bipolar Transistors (GaAs HBT).However, other semiconductor materials may also be used.

[0035]FIG. 3 illustrates an exemplary use of the radio frequency PAmodule for digital wireless communications in accordance to the presentinvention. The wireless communication device 300 can be a PDA, a WLANadaptor, or a cellular phone. The wireless communication device 300includes a base band processor core 320, RF transceivers 330, PA module14, and a 50-ohm impedance transmission line or micro strip 340connected to antenna 350.

[0036] A base band chip generates digitally modulated signals. Thefrequency is up-converted by a RF transceiver to a RF frequency bandsuitable for transmitting. The RF signal is amplified by the PA module14 for transmitting by the antenna. The PA module can be turned ON/OFFby the power control signal. The Vmode control (Pin 10) is used tocontrol and internal settings of the bias circuits by the base bandprocessor 320 which has the knowledge of the digital signal modulationtype and the linear output requirement. For example, when the device istransmitting high power, the Vmode control pin set the power amplifieroperating in high current to minimize output distortion. When the deviceneeds to transmit low power, the Vmode control pin 10 sets the poweramplifier with low current to conserve battery life.

[0037] The Power Sensor 26 measures the output RF power, which can beadvantageously used externally to the PA module. For example, the outputof power sensor can be used by the baseband processor 320 to set thetransmitting power level for the wireless device by varying the RF inputsignal to PA module.

[0038]FIG. 4 is a diagram of the pin-out and the footprint of the PAmodule in accordance with the present invention. The pin-out 100 showsthe bottom side of the PA module that includes a multitude of metalelectrodes and an insulating substrate. The physical metal pads 101,103, 106, 108 in FIG. 4 correspond to grounding Pins 1, 3, 6, 8 of thecircuit diagram in FIG. 2. The center ground 110 in FIG. 4 correspondsto 210 in FIG. 2.

[0039] The center ground 110 serves as major path for dissipating heatgenerated by the amplifiers. To keep the power amplifier run withoutexcessive temperature, it is important to minimize the heat transferresistance of the power amplifier to external space on printed circuit.It is also desirable to have minimal electrical resistance for thecurrent flowing between the center ground 110 to the ground of thecircuit board of the wireless device.

[0040] In the typical application for a wireless communication device,the PA module 14 is electrically mounted to a printed circuit board 400in the wireless communication device. The circuit board includes agrounding circuit design at the location where the PA module is mounted.The grounding circuit design consists of a metal land 410 and fourconnecting metal lands 401, 403, 406, and 408 adjacent to the fourcorners of 410. When the PA module is mounted to the printed circuitboard 400, pins 110, 101, 103, 106 and 108 on the bottom surface of thePA module are mated and connected to 410, 401, 403, 406 and 408,respectively.

[0041] The metal circuit 410, 401, 403, 406 and 408 are furtherconnected to a ground plane layer of the circuit board, typically belowthe RF signal layer, by “via holes” 420. The metal structure togetherwith the via holes illustrated in FIG. 4 enables effective currentflowing from the bottom conductive layer of the amplifier IC chip to thecentral metal land 410, out to the metal land 401, 403, 406, 408, andcontinuing down to the ground plane layer by the “via holes” 420.

[0042] The grounding structure also provides efficient heat dissipationfrom the amplifier IC chip in a similar fashion. The design describedabove is used advantageously to enhance heat transfer capability so theheat can be dissipated horizontally from the center as well asvertically by metal circuit 410, 401, 403, 406, 408 and via holes 420.Both the horizontal and the vertical means of metal circuits togetherprovide a good 3-dimensional topology for heat dissipation path. Thetypical mechanical dimensions and electrical characteristics of anembodiment for the present invention are illustrated in FIG. 5 and FIG.6, respectively.

[0043]FIG. 5 is an exemplary substrate layout. The power amplifiermodule is encapsulated in a plastic package with dimensions of about 5millimeters in length, about 5 millimeters in width and about 1.5millimeters in height. The central conductive land on the bottom sidehas dimensions of about 2.8 millimeters in length and about 2.8millimeters in width. The first, second, third and fourth ground padspositioned at each corner of the power amplifier module have typicaldimensions of about 1.7 millimeters in length and about 0.6 millimetersin width. The radio frequency input pad, the radio frequency output pad,the radio frequency power sense pad, the power supply pad, and the powercontrol pad have typical dimensions of about 0.6 millimeters in lengthand about 0.6 millimeters in width. The center-to-center distancebetween the radio frequency the power supply pad, and the power controlpad have a dimension of about 1.4 millimeters. The typical distance fromthe peripheral edges of the power amplifier module to wherein the first,second, third and fourth corner ground pads, the radio frequency inputpad, the radio frequency output pad, the radio frequency power sensepad, the power supply pad, and the power control pad is about 0.1millimeters. The typical distance from the radio frequency input pad andoutput pad to adjacent ground pads is about 0.4 millimeters.

[0044]FIG. 6 is an exemplary electrical response table showing thecharacteristics as follows: Key Electrical Characteristics Parameter MinTypical Max Unit Condition Operating Power 2.8 3.3 3.6 V Supply VoltageFrequency Range 5.150-5.825 GHz P1dB 26 dBm Small-signal Gain 30 dBOutput −37 dBc Pout = 20dBm Harmonics Output Noise −135 dBm/Hz LevelImpedance of 10 K Ohms Power Sensor Power Control- 2.87 V Enable PowerControl- <0.5 V Disable Power Control 4.0 mA Vcc = 3.3V, Current Vpc =2.87V Quiescent Current 100 mA Vcc = 3.3V, Vpc = 2.87V Input VSWR <2:1DC Supply 170 mA Pout = 20dBm Current

[0045] In the embodiment of FIG. 6, the module has a gain is about 30dB. The circuit is operated by a single DC power supply with a voltageranging from 2 to 5 volts. The amplifier is turned ON by with about 2.8volts applied to the power control pad, and the amplifier is turned OFFwith about less than 0.5 volt applied to the power control pad. Theoutput of the power sense pad ranges from 0 to 3 volts. The radiofrequency can be can be range between about 5 GHz to about 6 GHz orbetween about 2.4 GHz to 2.5 GHz.

[0046] Although specific embodiments of the present invention have beenillustrated in the accompanying drawings and described in the foregoingdetailed description, it will be understood that the invention is notlimited to the particular embodiments described herein, but is capableof numerous rearrangements, modifications, and substitutions withoutdeparting from the scope of the invention. The following claims areintended to encompass all such modifications.

What is claimed is:
 1. A power amplifier module for amplifying radiofrequency signals, comprising: first, second, third and fourth groundpads positioned at each corner of the power amplifier module; a groundpad located at the center of the power amplifier module; a radio inputpad positioned between the first and second corner ground pads; a radiooutput pad positioned between the third and fourth corner ground pads; aradio frequency power sense pad positioned to the power amplifiermodule; a power supply pad positioned to the power amplifiers module; apower control pad positioned to the power amplifier module; and a radiofrequency power amplifier circuit centrally positioned on the poweramplifier module, the power amplifier having an input coupled to theradio frequency input pad and an output coupled to the radio frequencyoutput pad.
 2. The module of claim 1, further comprising: a radiofrequency linear power amplifiers with multiple stages of transistors;an input match circuit coupled to the radio frequency input pad; anoutput match circuit coupled to the radio frequency output pad; a powersensor circuit coupled to the radio frequency power sense pad; and abias circuit coupled to the power control pad.
 3. The module of claim 1,wherein the power amplifier circuit controls quality of the radio signaloutput including error vector magnitude (EVM) and spectrum mask fordigitally modulated signals.
 4. The module of claim 1 wherein the first,second, third and fourth ground pads are elongated.
 5. The module ofclaim 1 wherein the bias circuit is controlled by feedback from thepower sensor signal.
 6. The module of claim 1, wherein the poweramplifier module has an electrically conducting base, comprising acentral conductive land on the module to bond with the electricallyconductive base of external grounding circuit, said central conductiveland connected with the first, second, third and fourth corner groundpads.
 7. The module of claim 1, wherein the power amplifier module isencapsulated in a plastic package with dimensions of about 5 millimetersin length, about 5 millimeters in width and about 1.5 millimeters inheight.
 8. The module of claim 1, wherein the central conductive land onthe bottom side has dimensions of about 2.8 millimeters in length andabout 2.8 millimeters in width.
 9. The module of claim 1, wherein thefirst, second, third and fourth corner ground pads positioned at eachcorner of the power amplifier module have dimensions of about 1.7millimeters in length and about 0.6 millimeters in width.
 10. The moduleof claim 1, wherein the radio frequency input pad, the radio frequencyoutput pad, the radio frequency power sense pad, the power supply pad,and the power control pad have dimensions of about 0.6 millimeters inlength and about 0.6 millimeters in width.
 11. The module of claim 1,wherein the center-to-center distance between the radio frequency thepower supply pad, and the power control pad have a dimension of about1.4 millimeters.
 12. The module of claim 1, wherein the distance fromthe peripheral edges of the power amplifier module to wherein the first,second, third and fourth corner ground pads, the radio frequency inputpad, the radio frequency output pad, the radio frequency power sensepad, the power supply pad, and the power control pad is about 0.1millimeters.
 13. The module of claim 1, wherein the distance from theradio frequency input pad and output pad to adjacent corner ground padsis about 0.4 millimeters
 14. The module of claim 2, wherein the gain isabout 30 dB.
 15. The module of claim 2, wherein the circuit is operatedby a single DC power supply with a voltage ranging from 2 to 5 volts.16. The module of claim 2, wherein the amplifier is turned ON by withabout 2.8 volts applied to the power control pad, and the amplifier isturned OFF with about less than 0.5 volt applied to the power controlpad.
 17. The module of claim 2, wherein the output of the power sensepad ranges between 0 to about 3 volts.
 18. The module of claim 2,wherein the radio frequency is between about 2.4 GHz to about 2.5 GHz.19. The module of claim 2, wherein the radio frequency is between about5 GHz to about 6 GHz.
 20. A wireless communication device fortransmitting and receiving radio frequency signals, comprising: a) apower amplifier module for amplifying radio frequency signals,comprising: first, second, third and fourth corner ground padspositioned at each corner of the power amplifier module; a radiofrequency input pad positioned between the first and second cornerground pads; a radio frequency output pad positioned between the thirdand fourth corner ground pads; a power amplifier circuit centrallypositioned on the power amplifier module, the power amplifier having aninput coupled to the radio frequency input pad and an output coupled tothe radio frequency output pad; and b) an antenna adapted to receive anoutput radio frequency signal from the power amplifier circuit.